I've been using a metal stock tank for close to 5 yrs. Love it. It's 120 gallon tank and I keep 7 goldfish in it. I was nervous at first, but now I wouldn't use anything else. It's got plenty of surface area compared to depth of tank; very important for goldfish. I keep it inside the house though. Soon, I'm going to upgrade and get a 250 gallon; yep, going to keep it inside too.

I sealed the valve with silicon; never had a problem with rust or leaking. I've enjoyed decorating around the tank. It's my indoor pond.

To avoid floating issues, keep water table low.
goldfish emergency